Tracking Real Time Changes in Working Memory ...

Tracking Real Time Changes in Working Memory Updating and Gating with Event-Based Eye-Blink Rate Rachel

1,3 Rac-Lubashevsky

, Heleen, A.

4 Slagter

and Yoav

2,3 Kessler

1Department

of Brain and Cognitive Sciences 2Department of Psychology 3 Zlotowski Center for Neuroscience 4Brain and Cognition, Department of Psychology, and Amsterdam Brain and Cognition (ABC) [email protected] 1,2,3 Ben-Gurion University of the Negev, Beer-Sheva, Israel 4University of Amsterdam, the Netherlands

Introduction

Experiment 3 Method and Results

Effective working memory (WM) functioning depends on the gating process which regulates between maintenance and updating in WM [1-3]. Keeping the gate closed enables robust maintenance within WM. In contrast, opening the gate allows WM to be updated with perceptually available input.

Aim: In this experiment we wished to extend the gating model and examined whether gating is stimulus or context driven?

Inter trial interval = 4.5sec-RT

Aims The present study used a novel method of event-based eye-blink rate (ebEBR), which presumably reflects phasic striatal dopamine activity [5-8], to examine how the cognitive processes of gating and updating separately facilitate flexible updating of WM contents and the potential involvement of dopamine in these processes. Real-time changes in eye-blinks were tracked during performance on the reference-back task [4], in which demands on these two processes are independently manipulated.

Method

The sequence length of each trial-type was random. A cue was presented before the stimulus as an empty colored frame for 4sec. The cue indicated the upcoming trial type.

The reference-back paradigm

Inter trial interval = 2sec

Cue locked analysis: Larger switch cost was observed in the first half of the segment than in the second half (0.03 vs. -0.003 ebEBR, respectively) F(1,20)=5.05, p=.04, ηp2 =.20. This switch cost was only observed in comparison trials, F(1,20)=11.89, p=.002, ηp2 =.37 but not in reference trials, F(1,20)=1.90, p=.18, ηp2 =.09 None of the other effects were significant. (N=21)

In each of the following trials, participants had to indicate whether the stimulus was the same as or different than the most recent reference (red) trial. Thus reference trials require updating of WM while comparison trials require maintenance. The sequence length for each trial-type was 4 trials.

Voltage

Stimulus locked analysis: The ebEBR pattern did not differ between the two segment parts. The main effects of Trial-Type and Switching were significant as in the original analysis. However, The two-way interaction between Trial-Type and Switching was marginally significant this time, F(1,20)=3.91, p=.06, ηp2 =.16, reflecting significant switch cost only in reference trials, F(1,20)=11.96, p=.002, ηp2 =.37 but not in comparison trials, F(1,20)=.74, p=.40, ηp2 =.04.

seconds

Eye blinks were recorded using a BioSemi Active Two system. Two external electrodes were placed above and below the right eye. Eye blink detection was done using a MATLAB code based on the VEOG channel. ebEBR per second was calculated for each condition.

Experiment 1 results (N=19)

slower RT was observed in reference trials than in comparison trials, F(1,18)=42.26, p